1. Field of the Invention
The present invention relates to a photo printer, and more particularly, to a photo printer with sensors arranged along a length of a ribbon for detecting the ribbons position.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of a conventional ink ribbon positioning system 10. FIG. 2 is a block diagram of a conventional color printer 50. FIG. 1 and FIG. 2 show the Taiwan Patent No. 399016 xe2x80x9cINK RIBBON POSITIONING SYSTEM OF A COLOR PRINTERxe2x80x9d. The ink ribbon positioning system 10 is used for identifying the position of a color ink ribbon 12 of the color printer 50. The ink ribbon 12 is installed inside a ribbon cartridge (not shown) in a windable manner, and comprises a plurality of sequentially arranged dye regions 14. Each of the dye regions 14 comprises four dye frames 16, 18, 20, 22 for separatelycarrying yellow, magenta, cyan, and over coating dye. The ink ribbon 12 also comprises opaque regions 24 installed at the front and rear ends of the dye regions 14.
The ink ribbon positioning system 10 comprises a light source 32 installed at one side of the ink ribbon 12 for emitting a light beam 34 of a predetermined color toward the ink ribbon 12 and an optical sensor 36 installed at the opposite side of the ink ribbon 12 fordetecting the light beam 34 passed through the ink ribbon 12 and generating a corresponding output voltage. The ink ribbon positioning system 10 also comprises an identification device 38 for identifying positions of the dye region 14 of the ink ribbon 12 and the dye frames 16, 18, 20, 22 inside the dye region 14 according to the output voltages generated by the optical sensor 36 and generating corresponding position signals. The light beam 34 emitted by the light source 32 has different penetration rates for each of the four dye frames 16, 18, 20, 22 inside the dye region 14 and for the opaque region 24. Therefore, when two adjacent dye frames pass by the optical sensor 36 sequentially, the optical sensor 36 will generate different output voltages.
The color printer 50 comprises a winding mechanism 52 for winding the ink ribbon 12 inside the ribbon cartridge so that each of the dye frames 16, 18, 20, 22 inside the dye region 14 pass by a thermal print head 54 sequentially, the thermal print head 54 for transferring the different colors of dye on the dye frames 16, 18, 20, 22 onto a photo paper (not shown) sequentially, and a control circuit 40 for controlling operations of the winding mechanism 52 and the thermal print head 54 according to the position signals generated by the identification device 38 so as to form a desired pattern.
Because the light beam 34 emitted by the light source 32 has different penetration rates for each of the dye frames 16, 18, 20, 22 and the opaque region 24, as two adjacent dye frames pass by the optical sensor 36 in sequence, the optical sensor 36 will generate different output voltages. The identification device 38 will identify the positions of the dye region 14 and the dye frames 16, 18, 20, 22 inside the dye region 14 according to the corresponding output voltages generated by the optical sensor 36, and will generate corresponding position signals. The control circuit 40 will control the winding mechanism 52 to wind the ink ribbon 12 according to the position signals generated by the identification device 38 so as to pass the ink ribbon 12 by the thermal print head 54 for sequentially transferring dyes onto the photo paper.
The identification device 38 differentiates the positions of each of the four frames 16, 18, 20, 22 inside the dye region 14 according to the light beam having different penetration rates for each frame. The identification device 38 comprises three comparators 42, 44, 46 with reference voltages between the four dye frames 16, 18, 20, 22 and the opaque region 24 so as to discern the four distinct output voltages and generate corresponding position signals for identifying the positions of the dye frames 16, 18, 20, 22 inside the dye region 14 of the ink ribbon 12. However, the yellow dye frame 16 and the over coating dye frame 22 will generate the same output voltage, so the identification device 38 has to discern orders of the other dye frames (the magenta dye frame 18 and the cyan dye frame 20) first to differentiate the yellow dye frame 16 from the over coating dye frame 22. In addition, a particular barcode is printed at a front end of the yellow dye frame 16 and the over coating dye frame 22 respectively to distinguish the two. This causes the color printer 50 to need more time to identify the initial position of the ink ribbon 12 (the initial position of the yellow dye frame 16) when the color printer 50 prints at the initial position of the yellow dye frame 16. It also increases the amount of parts used, resulting in higher production costs.
It is therefore a primary objective of the present invention to provide a color printer with sensors arranged along a length of a ribbon for detecting the ribbons position to solve the above-mentioned problems.
In the claimed invention, the color printer comprises an ink ribbon capable of moving in a predetermined direction. The ink ribbon has a plurality of dye regions sequentially arranged in the predetermined direction on the ink ribbon. Each dye region includes a plurality of dye frames for carrying dye of different colors,a print head for transferring the dye of different colors stored in the dye frames onto an object to form a desired pattern,a ribbon driving device for causing the ribbon to move in the predetermined direction, a controller for controlling the color printer, and a plurality of optical detecting devices mounted adjacent to the ink ribbon and arranged sequentially along the predetermined direction. When each of the optical detecting devices senses a dye frame, at least two output signals are detected. Each output signal is defined as a phase. A position of the ink ribbon is discerned by the controller according to the phase and phase-to-phase variation recorded by the optical detecting devices when the controller commands the ribbon driving device to move the ink ribbon.
The ink ribbon positioning system in the present invention can search for an initial position of the dye frame of the ink ribbon according to the different phase-to-phase variations generated by the light sources and the photo sensors of the optical detecting devices without any identification devices, parts for measuring voltage variations, or particular barcodes to identify the ink ribbon, resulting in decreasing costs.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the multiple figures and drawings.